Examples of currently-used liquid crystal display devices include one with a so-called back light device of an edge light type (side light type) in which light sources are disposed on a rear face end of a liquid crystal panel. In the back light device of the edge light type, light from the light sources such as LEDs enters into a light guide plate, propagates inside of the light guide plate, and then exits toward the liquid crystal panel. At this time, a back light device described in Japanese Unexamined Patent Application Publication No 2012-234675 is disclosed as one technique of achieving uniform luminance of light entering into the light guide plate.
The back light device includes a plurality of LEDs spaced apart at a relatively large interval along a light incident end face of a light guide plate. With such a configuration, portion around the light incident end face of the light guide plate that faces adjacent LEDs is likely to be a dark area. Accordingly, the light guide plate includes recesses each depressed to be a V-shape, the recesses being formed at a portion of the light incident end face that faces the adjacent LEDs. The recesses are each configured by a V-shaped inclined face. Light entering the light guide plate from the LEDs is partially reflected by the inclined face, and reflected light reaches regions that are likely to be the dark area described above. Accordingly, even when the adjacent LEDs are spaced apart by a long interval, suppression in production of the dark area around the light incident end face is obtainable in the light guide plate.
The recesses of the light guide plate each include the planar inclined face whose inclination angle is set within a predetermined range. This causes light to be reflected toward the region that is likely to be the dark area. Consequently, if the recesses each include no inclined face as above, light reflected on the recesses is unlikely to reach the regions, so that production of the dark area described above is not suppressive. For instance, when a camera is disposed at a part of an outer periphery of a smartphone in application to the smartphone and the like, such is occasionally performed that an outer periphery of a liquid crystal display device is depressed, and the camera is disposed in the depressed portion. In this case, a recess having a curve along a contour of the camera and a recess surrounding the camera in a rectangular shape are formed on a light incident end face of the light guide plate. At this time, LEDs are arranged along a portion except for the recesses on the light incident end face. As a result, an interval between the adjacent LEDs across the recess becomes long, and thus portions around the light incident end face of the light guide plate that each face the adjacent LEDs are likely to become a dark area. On the other hand, it is difficult to apply the technique described in Japanese Unexamined Patent Application Publication No 2012-234675 to the light guide plate with such recesses for preventing production of the dark area around the light incident end face of the light guide plate.